The prevalence of obesity keeps increasing in industrialized countries. However, efficient treatments of this chronic disease are still lacking. A better understanding of the systems that regulate energy balance and eating behavior is mandatory to better understand the disease and find appropriate treatments. The endocannabinoid system (ECS) which comprises cannabinoid receptors, such as CB1 and CB2, endogenous ligands (named endocannabinoids) and specific biosynthetic and degradative pathways is a key system in the regulation of energy balance and obesity. Obesity is characterised by an hyperactivity of the system both in animal and humans. Moreover, the activity of the ECS is influenced by feeding status although only one study has only been performed in humans. The investigation of the ECS in humans needs invasive procedure (blood sampling or adipose or liver biopsy). The aim of our study is to evaluate a new tool for the ECS evaluation in humans i e the determinations of saliva concentration of endocannabinoids both in normal weight and obese subjects before and after food intake. Blood and saliva sampling will be performed after an overnight fast, one hour before, just before and one hour after a lunch in12 normal weight subjects and 12 obese characterised with anthropometric (Weight, height, BMI (Body Mass Index), waist circumference, blood pressure) and metabolic (glycaemia, insulin, lipid profile, liver profile) evaluations. The endocannabinoids concentrations will be measured with mass spectrometry in blood and saliva and gut hormones (PYY (peptide YY) and ghrelin) will be measured in plasma.